Monitoring Carbon Dioxide Floods Using Electrical Resistance Tomography (ERT): Sensitivity Studies

Abstract

We have conducted a numerical and physical modeling study to evaluate the sensitivity of electrical resistance tomography (ERT) to electrical resistivity changes caused by [Formula: see text] injection and sequestration in geologic reservoirs. We chose the Maljamar [Formula: see text] flood (pilot study) as a basis for our numerical modeling study. We also constructed physical models consisting of blocks of various materials inserted in a water tank to evaluate some of the conclusions of the numerical study. This study quantifies the effects of a variety of factors that affect the resolution and accuracy of the ERT method, under realistic conditions of scale, contrast, and measurement error. It considers scenarios where vertical arrays of point electrodes are used and where metal-cased boreholes are used as long electrodes. Long electrode tomographs provide information such as the shape, location, and lateral extent of the flood. When point electrode arrays or horizontal wells are available, the approximate vertical extent of the flood and coarse estimates of sequestered [Formula: see text] volume may be deduced. Results from physical models support trends observed in the numerical study. Based on this study, we suggest that the ERT method can help confirm the containment of [Formula: see text].